وَقَالُوا۟ مَا هِىَ إِلَّا حَيَاتُنَا ٱلدُّنْيَا نَمُوتُ وَنَحْيَا وَمَا يُهْلِكُنَآ إِلَّا ٱلدَّهْرُ وَمَا لَهُم بِذَٰلِكَ مِنْ عِلْمٍ إِنْ هُمْ إِلَّا يَظُنُّونَ
"They said: Life is nothing but this life of ours in the world; we die and we live. Nothing destroys us but dahr. Yet they have no knowledge of this whatever; they only conjecture."
1. Life is only this — there is no other life 2. We die and we live — the generations succeed one another 3. Nothing destroys us but dahr — the cause is time
And the answer is given not to the content of the claim but to what it rests on: wa mā lahum bi-dhālika min ʿilm — "they have no knowledge of this."
This is the clearest observation about method in the sūra, and I record it as my own reading: the verse does not say "you are mistaken"; it says "you are not saying this on the basis of knowledge." That is, the other side's claim is treated as a claim to knowledge, and that attribute is taken from it.
In hum illā yaẓunnūn — "they only conjecture." The opposition between ẓann and ʿilm is the axis the sūra has been building from the start: in verse 4 yūqinūn (those who know with certainty), in 5 yaʿqilūn, in 20 yūqinūn, and here yaẓunnūn.
The word means "long time, the age that goes on". The root was treated in al-Insān at 76/1 (hal atā ʿala'l-insāni ḥīnun mina'd-dahr). I do not repeat it here.
What belongs here is this: there the word occurred as a span, here it is named as an agent — "what destroys us".
I record this as an observation: the claim does not deny death; it charges death to time. That is, the observed fact (everyone dies) is correct; the cause assigned to it is what is being questioned. This meets the list of proofs in the sūra's first block at the very same point: the alternation of night and day was named there as a sign; here the same working is counted as an agent.